Previously, a 38-base-pair (bp) region in the 3' untranslated portion of the Saccharomyces cerevisiae iso-1-cytochrome c gene, was shown to be required for both normal CYC1 mRNA 3' end formation (Zaret and Sherman, 1982), and efficient transcription termination (Russo and Sherman, 1989). In another study, specific sequences such as TATATA, TACATA, and TAGTAGTA were shown to be involved in mRNA 3' end formation in S. cerevisiae (Russo et al., 1991). In this report, an in vivo plasmid stability assay has been utilized to show that these and related sequences are also involved in transcription termination, at varying efficiencies, and in an orientation-dependent manner. For example: the sequence TATATA appeared to terminate transcription almost as efficiently as the original wild type 38-bp region; whereas, the sequences TAGATATATGTAA and TACATA were less efficient, and TTTTTTTATA had little, if any, transcription termination function. In contrast, none of these sequences appeared to terminate transcription in the reverse orientation. Therefore, it appears that certain sequence signals capable of promoting mRNA 3' end formation in yeast, are also directly involved in transcription termination.